Update formlatest GraphQlTester changes

See spring-projects/spring-graphql#278

spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-graphql/src/test/java/smoketest/graphql/ProjectControllerTests.java

@@ -37,7 +37,7 @@ class ProjectControllerTests {
 	@Test
 	void shouldNotFindUnknownProject() {
 		this.graphQlTester.document("{ project(slug: \"spring-unknown\") { name } }").execute().path("project.name")
-				.valueDoesNotExist();
+				.pathDoesNotExist();
 	}
 
 }